1. Field of the Invention
The present invention relates to a light emitting device material which is useful as a fluorescent dye and a charge transporting material, and a light emitting device using the same. The light emitting device of the present invention can be applied to the fields of display elements, flat panel displays, backlights, illuminations, interiors, signs, billboards, electrophotographic machines, optical signal generators and the like.
2. Description of the Background Art
In recent years, there have actively been conducted researches of an organic thin-film light emitting device that emits light when an electron injected from a cathode and a hole injected from an anode recombine in an organic luminous body interposed between the electrodes. Intense interest has been shown toward this light emitting device because of such a feature that it is thin and capable of emitting high-luminance light under a low driving voltage and emitting multicolor light through selection of an emissive material.
Since C. W. Tang et al. of Eastman Kodak Company showed that an organic thin-film light emitting device emitted light at a high luminance, many research institutes have studied this technology. The typical structure of an organic thin-film light emitting device proposed by a research group of Eastman Kodak Company is such that a hole-transporting diamine compound, an emissive layer made of tris(8-quinolinolato)aluminum(III), and a cathode made of a Mg:Ag alloy are formed sequentially on an ITO glass substrate, and the device was able to emit green light of 1,000 cd/m2 at a driving voltage of about 10 V (see Applied Physics Letters, USA, 1987, Vol. 51, No. 12, pp. 913-915).
One of the greatest problems with organic thin-film light emitting devices is to obtain luminance efficiency, color purity, and durability of a device at satisfactory levels simultaneously. With respect to a blue light emitting device, there are few blue emissive materials capable of providing a device that is excellent in luminance efficiency and color purity and has high reliability. For example, there have been disclosed technologies using, as a blue dopant material, a styrylamine derivative (see Japanese Unexamined Patent Publication No. 5-17765), a perylene derivative (see Japanese Unexamined Patent Publication No. 2003-86380), and an anthracene derivative (see International Publication No. 00/40586 Pamphlet). Moreover, technologies using a fluorene compound (see Japanese Unexamined Patent Publication No. 2007-39406 and International Publication No. 06/100896 pamphlet) for a blue light emitting device have been disclosed. However, all the technologies are insufficient in luminance efficiency, color purity, and durability.